Turbomachine Casing Asymmetric Stiffness Anti-Instability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The reduction of clearance between rotor and stator components in turbomachines leads to increased risk of contact-induced instability, resulting in blade vibrations and potential damage due to resonance phenomena, which existing solutions fail to adequately address by neglecting rotor/stator interactions.

Innovation Solution

A rotor/stator assembly with a casing featuring an anti-instability device comprising elements of different stiffness arranged along the circumference, breaking cyclic symmetry to inhibit specific vibratory modes, thereby preventing coupling phenomena without modifying the rotor or aerodynamic stream.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If clearance between rotor and stator is reduced to increase efficiency, then efficiency is improved, but contact-induced instability and blade vibrations occur

Engineering Contradiction:

ImproveefficiencyVSAvoidcontact-induced instability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces an asymmetric stiffness distribution in the stator casing by arranging elements of different stiffness values (k1, k2, k3, k4) around the circumference. This asymmetric configuration breaks the cyclic symmetry that would otherwise allow resonant vibratory modes to develop, thereby preventing contact-induced instability while maintaining reduced clearance for high efficiency operation.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by varying the stiffness of specific elements at different angular positions around the stator. Each element has a locally optimized stiffness value that contributes to the overall asymmetric stiffness distribution, allowing targeted modification of local dynamic characteristics to inhibit specific vibratory modes without affecting the entire structure uniformly.

Inventive Principle:

Principle #3Local quality

2Strength

If relief is performed at blade edges to limit damage, then blade damage is reduced, but performance deteriorates

Engineering Contradiction:

Improveblade damage resistanceVSAvoidperformance

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The patent applies preliminary anti-action by pre-configuring the stator casing with an asymmetric stiffness distribution that proactively prevents the development of resonant vibratory modes before contact occurs. This preventive approach eliminates the need for reactive blade edge relief modifications, thereby protecting blade strength while maintaining full aerodynamic performance.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If existing solutions are used to prevent vibration, then some vibration protection is provided, but rotor/stator interactions are not addressed

Engineering Contradiction:

Improvevibration protectionVSAvoidrotor/stator interaction coverage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent uses the stator casing as an intermediary element to prevent rotor/stator interaction instabilities. By modifying the stator's stiffness distribution, the invention indirectly controls the coupled rotor-stator vibratory behavior without requiring direct modification of the rotor or the aerodynamic flow field between them, thereby addressing rotor/stator interactions while maintaining system compatibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively eliminates the risk of instability and blade damage by inhibiting targeted vibratory modes, ensuring the rotor/stator assembly operates safely and efficiently without affecting existing hardware or performance.

Implementation Method 1

the numbers of elements of the same stiffness being different from a multiple of the wave number of the vibratory mode to be inhibited of the bladed wheel

Methodology Applied

Scientific EffectVibratory modes: Vibration

Implementation Method 2

to prevent resonance phenomena by voluntary detuning of the bladed wheel

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

casing 10 coated with a layer of abradable material 12 on its inner face

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentEP2112326B1Turbomachine casing comprising a device preventing instability in the event of contact between the casing and the rotor

Publication Date: 2018.12.05 SAFRAN AIRCRAFT ENGINES SAS

Figure 1~4
Figure 3~6

AI summary

The casing (110) has an anti-instability device (120) provided on an inner surface of the casing for preventing instability during a contact between the casing and an impeller e.g. one-piece blade disc. The device has two types of elements (122, 124) placed along a circumference of the casing and presents different rigidity between the elements, where the two types of the elements are formed of two different abradable material layers of different Young's modulus. Number of elements of same rigidity is different from multiple of wave number of vibration mode of the impeller. An independent claim is also included for a method for preventing an occurrence of instability during a contact in a stator/rotor assembly of a turbo machine.